Comment by Kamikaze28

Mounting, dismounting and changing mounts will not disable the toy once activated.

The fireworks happen with every jump while you are mounted and the toy is active (15 sec). Riding uphill, thus making each jump miniscule, while hammering your jump key will produce an absurd trail of fireworks behind you (screenshot submitted, pending approval).

Jumping while standing still (for example with the Champion's Treadblade) will not produce fireworks. Similarly, attempting to jump with mounts that perform their /mountspecial animation instead will also not produce fireworks.

The fireworks are somewhat random and multi-colored.

You cannot produce fireworks with a flying mount in zones where you can fly.

In response to the comment by Stormreave: yes, jumping out of water with any kind of ground mount triggers fireworks. It is worth keeping in mind though that purely aquatic mounts break when jumping out of the water, like the Subdued Seahorse.